Marriage and divorce are both bad for the waistline, new research suggests.

But while women tend to gain weight after their wedding day, men are most affected by marital breakdown.

Both kinds of “marital transition” can act as “weight shocks” that put on the pounds, a study has found.

“Divorces for men and, to some extent, marriages for women promote weight gains that may be large enough to pose a health risk,” said study leader Dmitry Tumin, from Ohio State University in the US.

The likelihood of major weight gain after marriage or divorce increased most for people past the age of 30.

“For someone in their mid-20s there is not much difference in the probability of gaining weight between someone who just got married and someone who never married,” said Mr Tumin, a doctoral student in sociology. “But later in life, there is much more of a difference.”

The findings were presented at the annual meeting of the American Sociological Association in Las Vegas, US.

Researchers used survey data on more than 10,000 people to investigate whether marriage and divorce led to weight gains or losses.

They took account of a wide range of other factors that can influence changes in weight, including pregnancy, poverty, socioeconomic status and education.

Both men and women who married or divorced were more likely than never-married individuals to experience a small level of weight gain after a “marital transition”.

The results tie in with other research on how marriage affects men and women, say the scientists.

“Married women often have a larger role around the house than men do, and they may have less time to exercise and stay fit than similar unmarried women,” said Zhenchao Qian, professor of ­sociology at Ohio State ­University.

“On the other hand, studies show that married men get a health benefit from marriage, and they lose that benefit once they get divorced, which may lead to their weight gain.”

He added: “From age 22 to 30, the effect of marital transitions on weight is not very clear. But both marriages and divorces increase the risk of weight changes from about age 30 to 50, and the effect is stronger at later ages.”

Marriage or divorce may come as a greater shock to older people settled into certain patterns of physical activity and diet, according to the researchers.

“As you get older, having a sudden change in your life like a marriage or a divorce is a bigger shock than it would have been when you were younger, and that can really impact your weight,” said Mr Tumin.